We hypothesize that low-dose fenoldopam (a novel dopaminergic agonist) will directly augment renal plasma flow through selective renal vasodilation in subjects with SIRS, without affecting the systemic or pulmonary circulations. We will determine the effects of low-dose fenoldopam on renal perfusion (measured by PAH clearance) in critically ill patients with SIRS. We will also determine the effects of low-dose fenoldopam on systemic and pulmonary hemodynamic parameters, and selected renal functions, as well as measuring plasma fenoldopam samples to determine simple pharmacokinetic parameters in this population. This is an investigator-initiated study. The sole involvement of the manufacturers of fenoldopam (Neurex Division/Elan Pharmaceuticals) will be limited to the complimentary provision of study drug.